Investigators in Russia say five men have been arrested in connection with the attacks on two Islamic spiritual leaders in the mainly Muslim republic of Tatarstan.
Mufti Ildus Faizov suffered broken legs and other injuries in a car bombing on July 19 in the Tatar capital, Kazan.
The attack came an hour after his former deputy and close associate, Valiulla Yakupov, was shot dead in a different district of the city.
One Uzbek citizen and four Tatars have been arrested in connection with the attacks, including the owner of a travel company specializing in trips to the annual Muslim hajj pilgrimage.
Russian Investigative Committee spokesman Vladimir Markin suggested the attacks could be linked to Faizov's control over hajj funding.
The Investigative Committee spokesman said Faizov put Idel-Hajj's financial flows under his direct supervision after being appointed mufti in January 2011.
"After Faizov was elected chief mufti of Tatarstan, he adopted a tough stance on organizations professing radical Islamic views in the republic," Markin said. "Faizov was blocking the activities of organizations propagating this trend in Islam. In addition, he took under his supervision the flow of money to Idel-Hajj, which was sending Muslims to [the hajj in] Mecca. He had a conflict related to that with the head of that organization, who threatened Faizov."
The brazen, mid-morning attacks are seen as a rarity in Tatarstan, which has witnessed little of the violence against religious leaders common in other Muslim-majority republics in Russia's North Caucasus.
Russian President Vladimir Putin said on July 19 that the attacks sent a "serious signal" to authorities. Putin noted an apparent lack of measures to protect the leaders.
Federal authorities have characterized the failed assassination attempt on Faizov as a terrorist attack.
Members of the Investigative Committee and the Federal Security Service participated in the July 20 arrests, alongside local police.
The body of Faizov's former deputy Yakupov will lie in state at a farewell ceremony on July 20. Police in the Tatar capital have been put on alert for further violence.
Yakupov, 49, had been a powerful member of Tatarstan's Muftiyat spiritual board for two decades and had recently become the head of its education department.
Both he and Faizov, also 49, were seen as having close ties to the Kremlin and had acted to centralize Tatarstan's Muslim structures.
Such moves were seen as an effort to discourage what they saw as more radical forms of Islam, such as Wahhabism, which has been blamed for a rise in sectarian violence in the restive North Caucasus.
Russian Orthodox Patriarch Kirill has expressed regret over the attacks on Faizov and Yakupov, saying the violence deals a blow to "traditional Islam" and "interreligious cooperation."
With reporting by Interfax, ITAR-TASS, and Reuters